p4a is not compatible with ndk >= 22

[obfusk]

From the changelog of ndk 22:

• The deprecated <NDK>/platforms and <NDK>/sysroot directories have been
  removed. These directories were merged and relocated into the toolchain during
  r19. The location of these contents should not be relevant to anyone,
  including build systems, since the toolchain handles them implicitly. If you
  are using a build system that hasn't adapted to the changes introduced in NDK
  r19, file a bug with your build system maintainer. See the [Build System
  Maintainers Guide] for information on using the NDK in your own build system.